CPSW_CPDMA_TX_HDP
txchan, cpsw_read_4(sc, CPSW_CPDMA_TX_HDP(txchan)));
cpsw_read_4(sc, CPSW_CPDMA_TX_HDP(0)));
#define CP_OFFSET (CPSW_CPDMA_TX_CP(0) - CPSW_CPDMA_TX_HDP(0))
cpsw_write_4(sc, CPSW_CPDMA_TX_HDP(i), 0);
sc->tx.hdp_offset = CPSW_CPDMA_TX_HDP(0);